More recently I've been using Adam's Graphene coating, just from an ease-of-use perspective. Before that, I used Optimum Gloss Coat. Both of these products are consumer-level "coatings". You need to prep the surface properly (clay, decontaminate paint, polishing if necessary, alcohol wipe) and then apply. On a weekend car, you can get 18+ months of longevity. The Gloss Coat can also be topped pretty easily with a spray sealant or whatever you want to maintain the car with on a regular basis.
There are lots of good coatings on the market for consumers, but I like the two above for their combination of easy to use, longevity, and of course price. For < $100 and some elbow grease, really hard to complain.